Tackling invasive non-native species (INNS) to help protect our wildlife

Water companies like ourselves are highly vulnerable to Invasive Non-Native Species (INNS), not only as landowners, but as significant landowners of wetland habitats - 40% of INNS are aquatic and are particularly problematic to deal with.

Non-native species are plants and animals that have been moved from their place of origin into Britain by humans (intentionally or accidentally). There's thought to be around 2000 non-native species in Britain.

Invasive non-native species (INNS) are non-native species which have a negative impact on the environment, economy or health of the place they've been moved to. In Britain, it's estimated that 10% of the non-native species are invasive - that's around 200 species, and the number is increasing.

A serious threat to biodiversity

Amongst habitat loss, fragmentation, pollution and climate change, INNS are one of the topmost serious threats to biodiversity. Recordings show that around 40% of Britain’s 200+ registered INNS are known to be aquatic. For us, that causes serious concern.

We carry out detailed surveys to identify INNS and have identified priority sites, species and activities. We are also reviewing region-wide risks.

Japanese knotweed

Japanese knotweed

This resilient, deep-rooted perennial is listed by the World Conservation Union as one of our planet’s worst invasive species. It has huge potential to cause significant structural damage at our treatment works and weirs. 

We’re monitoring knotweed on our sites via digital mapping technology and are working closely with ecological management experts, Ebsford Environmental, towards viable management solutions, including spraying it.

Himalayan Balsam

Himalayan balsam

This plant has quickly become one of the UK's most invasive weed species. Colonising in riverbanks and damp areas it can out-compete native plants for pollination and can reduce insect numbers. It can cause erosion, increase sedimentation, and affect water quality.

We support Hampshire and the Isle of Wight Wildlife Trust and volunteers to control this plant at two sites - Ampress WTW and Little Avon.

Crassula waterweed

Crassula and Nuttall’s waterweed

A powerful water weed that can affect oxygen levels, choke abstraction points and can cause health and safety issues for maintenance and recreation at reservoirs.

We are monitoring these species on or near two of our sites Longham Lakes and Blashford complex and liaise with South West Lakes Trust and Hampshire and the Isle of Wight Wildlife Trust regarding monitoring and biosecurity measures.

american signal crayfish

American signal crayfish

American signal crayfish carry a plague which kills our native crayfish. They can degrade reservoir banks by burrowing, causing sedimentation, reducing water quality and have a negative impact on fish.

We are working a range of stakeholders at one site the Blashford Lakes complex partners to implement biosecurity measures.

Our partnerships

In collaboration with our partners, we actively tackle the challenge of invasive non-native species on our water sites. We embrace innovative research and measures to prevent these species from establishing themselves, while also working closely with our partners to achieve a collective impact.

South West Lakes Trust logo Environment Agency logo Angling trust logo
CABI logo hampshire isle of wight wildlife logo NNSS logo

Simple steps to prevent the introduction of new or spread of established INNS

Check, clean + dry

Whenever you leave a lake, remember to check your equipment, boat and clothing for mud, aquatic animals or plant material. Clean everything thoroughly and dry items before using again as some invasive plants can survive up to two weeks in damp conditions.

Check, clean + dry image